Reconstruction of extensive long bone defects in sheep using resorbable bioceramics based on silicon stabilized tricalcium phosphate

In this study we evaluated the performance of Skelite, a resorbable bioceramic based on silicon stabilized tricalcium phosphate (Si-TCP), in promoting the repair of a large-sized, experimentally induced defect in a weight-bearing long bone sheep model. Eighteen 2-year-old ewes were used in this study. Animals were sacrificed at 3, 6, and 12 months. One animal entered a very prolonged follow-up and was sacrificed 2 years after surgery. Bone formation and scaffold resorption were evaluated by sequential x-ray studies, CT scans, histology, immunohistology, microradiography, and quantitative analysis of x-ray studies (optical density) and microradiographs (percentage of bone and scaffold area). Our data show an excellent implant integration and significant bone regeneration within the bone substitute over the course of the experiment. Progressive osteoclastic resorption of the biomaterial was also evident. At 1 year from surgery, the remaining scaffold was approximately 10 - 20% of the scaffold initially implanted, while after 2 years it was essentially completely resorbed. At the end of the observation period, the segmental defect was filled with newly formed, highly mineralized, lamellar bone.